Connecting classification with phylogeny


Connecting classification with phylogeny


Using phylogeny to trace the relatives of birds


Each tree is a hypothesis about the most likely path of evolution based on the data available




  • Critical innovations: Derived traits
    • adaptive traits that define new taxa
    • marked with ‘slashes’ on tree
    • ‘shared derived character’ in book
    • evolutionary novelties


  • Shared ancestral traits: a trait that is found in the ancestor of a group and all of the derived taxa have the trait


  • What makes a bird a bird?

Anatomy of a phylogenetic tree


How to draw phylogenies: branch shape and length


How to draw phylogenies: branch shape and length


Mapping traits on a phylogeny (review homology)


Convergent evolution in marine mammals (analogous traits)


How to use derived characters to infer phylogeny


How to use derived characters to infer phylogeny






  • Parsimony = Simplest solution is the likely path of evolution


  • A logical way to identify homologous and analogous traits


  • Minimize the # of evolutionary changes needed to explain your character data

How to use derived characters to infer phylogeny


Whale Evolution: A Case History




  • Phylogenetic trees based on morphology place whales outside of the artiodactyl group


  • Atiodactyl: mammals - cows, deer and hippos
    • hooves, even number of toes
    • unusual pulley-shaped ankle bone


  • Astragalus ankle bone is a shared derived trait for all artiodactyls

Whale Evolution: A Case History




  • How do we determine evol’n relationships?
    • morphology - presence/absence of weird ankle bone
    • DNA sequences - shared gene families


  • Depends on what data you have!
    • poor fossil records made this tricky


  • Molecular data suggests a closer relationship between whales and hippos…

Whale Evolution: Whales and Hippos share common ancestor